As a technology for enhancing the starting performance of an engine, a technology for reducing the fuel injection amount at an engine starting time as compared to that at the normal time is disclosed in Japanese Patent Laid-open No. Sho 64-56931. This technology is in view of the fact that the engine is often in a low-temperature state at the time of starting the engine and that, if the fuel in an amount comparable to that in the normal operation is injected notwithstanding the reduction in the amount of petroleum evaporated, the petroleum in liquid state would be deposited on a spark plug, leading to misfire.
On the other hand, a vehicle with an automatic engine stopping and starting system mounted thereon for stopping the engine in response to a predetermined vehicle stopping condition and, after the automatic stoppage, restarting the engine in response to a predetermined vehicle starting operation is disclosed in Japanese Patent Laid-open No. 2002-115578. In such a vehicle, when a throttle grip is operated to open after automatic stoppage of the engine, this operation is recognized as a vehicle starting operation and the engine is restarted.
In a system in which the engine is started in response to the operation of opening the throttle grip, if the fuel injection amount at the engine starting time is reduced as compared with that in the normal operation in the case where the throttle opening is enlarged by the driver at a vehicle starting time after automatic stoppage of the engine, the fuel amount may become comparatively insufficient and the fuel-air mixture may become lean, possibly resulting in a lowering in the starting performance of the engine.
A need exists for fuel injection control systems in which the starting performance of an engine from an automatic stoppage state of the engine is enhanced, in a vehicle with an automatic engine stopping and starting system mounted thereon.